Pendeo-epitaxy: A new approach for lateral growth of gallium nitride films

Abstract

Lateral growth of gallium nitride (GaN) films having a low density of dislocations and suspended from side walls of [0001] oriented GaN columns and over adjacent etched wells has been achieved without the use of, or contact with, a supporting mask or substrate. Pendeo-epitaxy is proposed as the descriptive term for this growth technique. Selective growth was achieved using process parameters that promote lateral growth of the $\{ 11\bar 20\}$ planes of GaN and disallow nucleation of this phase on the exposed silicon carbide substrate. The large horizontal/vertical growth rate ratio indicate that the diffusion distances and the rates of diffusion of the reactant species along the (0001) surfaces were sufficient to allow them to reach and move along the $\{ 11\bar 20\}$ surfaces before they were chemically adsorbed. A four-to-five order decrease in the dislocation density was observed via transmission electron microscopy in the free-standing laterally grown GaN relative to that in the GaN columns. Curvature of the $\{ 11\bar 20\}$ planes as they approached coalescence, and elongated voids below the regions of coalescence were formed. The use of optimized growth conditions or more closely spaced columns should eliminate these voids.